Roller Type hydrocushion mechanical tappet

ABSTRACT

A tappet comprises a foot having a convex cam contact surface and an axially extending hub, a tappet body having a lower body portion with a lower axial bore formed therein to receive the axially extended hub of the foot, and hydrocushions of oil between the foot, a thrust washer, and the lower portion of the tappet body. The cam contact surface operates in a frictional relationship with a cam lobe and the cam contact surface of the foot induces the foot to rotate about the centerline of the tappet. The hydrocushions of oil on each side of the thrust washer operate to reduce friction as the foot independently rotates axially about a centerline of the tappet body.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of Provisional Patent ApplicationSer. No. 60/742,080 filed Dec. 2, 2005, herein incorporated byreference.

FIELD OF INVENTION

This invention relates to engine tappets or lifters, and morespecifically, to new forms of mechanical tappets including roller endsthat interface with a cam.

BACKGROUND OF INVENTION

The tappet in an internal combustion engine is a well-known device, andis also commonly referred to as a lifter, valve lifter, or tappet. Forexamples of common forms of tappets, see William H. Crouse and Donald l.Anglin's Automotive Mechanics (McGraw-Hill 10th Edition), ISBN0-02-800943-6 at pp. 131, and 169-170 and Smokey Yunick's and LarrySchrieb's Power Secrets (S-A Design Books 1989) ISBN 0-931472-06-7 atpp. 76-80, both of which are incorporated herein by reference.

FIG. 1 depicts a typical tappet application for a push rod engine. Ingeneral, a lifter or tappet interacts directly with a rotating camshaftin the engine's valve train. That interaction begins the chain of eventsthat converts the rotary motion of the camshaft into the reciprocatingmotion of the engine's intake and exhaust valves. The amount ofhorsepower generated by an engine is related to how efficiently thevalve train operates. Indeed, it is common knowledge that, of all theadjustments that can be made to an internal combustion engine,adjustments to the valve train have the greatest impact on increasinghorsepower.

In general, the more efficiently air enters and combusted gas exits anengine, as controlled by the opening and closing of the intake andexhaust valves, the more horsepower the engine will produce. “Lifting,”or opening the valves as high and as fast as possible, and closing thevalves as fast as possible, are necessary to obtain efficient air andgas flow, and to achieve optimum horsepower. “High lift” is generallyobtained by designing a camshaft having aggressive cam lobes with steepflank angles. Consequently, in high-performance applications, a tappetmust be able to reliably negotiate the contour of an aggressive cam lobeat extremely high rpm's. In addition, the tappet must be durable andcapable of withstanding extreme frictional forces and high valve springpressures.

Pushrod type internal combustion engines typically use one of four typesof tappets or lifters: the flat mechanical tappet, the mushroom tappet,the roller tappet, or the hydraulic tappet. Each of these types oftappets or lifters is discussed briefly below.

The single piece flat mechanical tappet is inexpensive, simple toproduce, and reliable in stock environments, and has been the industrystandard for years. In high performance applications, however, the flatmechanical tappet has several limitations. First, the flat mechanicaltappet requires an extensive and detailed break-in procedure. Thebreak-in procedure typically includes: (1) polishing the lifter footwithout disturbing the contour of its convex foot; (2) coating thecamshaft lobes with a high performance lubricant; (3) preheating theengine oil before starting the engine, (4) installing light weight valvesprings; (5) starting and running the engine for about thirty minutes atabout 2500 rpm's to ensure that adequate oil circulation is present inthe valve train, and that the tappets are broken in slowly; (6) aftershutting down the engine, installing the proper valve springs. Thistedious process is necessary to obtain optimum performance from both thetappets and camshaft. Second, mechanical tappets do not work well inhigh performance applications using aggressive camshafts characterizedby lobes having steep opening and closing flanks.

The “mushroom tappet” was developed in an effort to address some of thelimitations of the standard mechanical tappet, particularly for use withaggressive camshaft designs. The mushroom tappet uses a foot with alarger diameter than the body of the tappet, which allows it to moreeasily negotiate the steeper flank angles of aggressively designed camlobes. However, several drawbacks are also associated with mushroomtappets. First, before a mushroom tappet can be used, the engine blockmust usually be machined to ensure adequate clearance with the enlargedtappet foot. Second, the enlarged mushroom tappet foot requires that thetappet be inserted and removed from the bottom of the engine block,thereby complicating repairs or maintenance on the valve train. Third,even the mushroom tappet is characterized by relatively high frictionrates requiring significant lubrication.

Moreover, all mechanical tappets are designed to rotate in their bore.The rotation is induced when the convex surface of the lifter foot is incontact the tapered, rotating, cam lobe. The rotation of the lifter ortappet in its bore is necessary to avoid prematurely wearing the lifterfoot and cam lobe. However, several additional disadvantages areassociated with tappet rotation. First, as the lifter rotates,considerable friction is generated between the surface area of theinside diameter of the lifter bore and the surface area of the outsidediameter of the lifter body. Thus, mechanical tappets have relativelyhigh friction rates that often require extensive modifications to theengine to increase the oil flow to the cam lobes and upper valve trainin high-performance applications. Secondly, because mechanical tappetsrotate, the use of “Rev Kits” (discussed below) has not been successful.Third, because the entire mechanical lifter rotates, it is not possibleto use an offset pushrod cup, which is often needed to gain additionalpushrod/cylinder head clearance in some applications. More specifically,offset pushrod cups are typically used in applications where the intakeports of the engine block have been bored to a larger size thussometimes creating a less than zero clearance between the pushrod andengine block.

To reduce the adverse effects of friction between the tappet foot andcam lobe, it is highly desirable to make mechanical tappets that areboth light and strong, thereby reducing friction. However, the tappetmust still be strong enough to withstand the extreme pressures exertedfrom the valve springs and cam lobe, and durable enough to withstand therotational forces between the cam lobe and cam foot. As a result, manytypes of light-weight, exotic, and expensive materials have been used tofabricate tappets. The optimum solution is one that would be able toutilize two different metals in the lifter. This would make it possibleto use one type of metal for the lifter body, and one type for thelifter foot. However, the typical one-piece design of a mechanicaltappet dictates using the same material for the entire lifter body.

The “roller tappet” was developed in large part to overcome the manydisadvantages of the mechanical tappet. Roller tappets reduce frictionbetween the cam lobe and lifter foot, thereby reducing lubricationrequirements. Thus, roller tappets are desirable in high performanceapplications, as they can maintain valve train stability at high rpm'sand aggressive camshaft designs. However, they likewise have severaldrawbacks.

First, many race sanctioning bodies do not allow the use of rollertappets. Second, to achieve optimum performance with roller tappets, itis necessary to install an anti-rotational device and Rev Kit, therebyfurther increasing the number of valve train components, as well as thelikelihood of failure. If failure occurs in a roller tappet, typicallythe results are instantly fatal to the engine.

A fourth common form of lifter is a hydraulic lifter. Hydraulic liftershave several advantages over both mechanical lifters and roller lifters.Hydraulic lifters automatically compensate for any clearance changescaused by temperature variation or wear. Thus, they should never needadjustment. Also because there is no clearance between the lifter footand the cam lobe, hydraulic lifters are extremely quiet while inoperation when compared to either mechanical or solid lifters.Mechanical or roller lifters need to have some clearance or “lash”between the lifter foot and the cam lobe to act as a cushion to allowfor any tolerance changes due to thermal expansion or contractionencountered during repeated engine cycles.

However, hydraulic lifters also have some undesirable qualities.Hydraulic lifters are only as reliable as the cleanliness of the engineoil. Thus, if any dirt is present in the oil, the lifter will notcompress or decompress properly, and valve and camshaft damage wouldsoon result. Hydraulic lifters also do not work well at high rpm's,because the lifters have a tendency to “pump up” as the rpm's increase.In other words, as engine rpm's increase, more oil is introduced intothe oil chamber, preventing the lifter from compressing anddecompressing, and adversely impacting the stability of the valve train.The result is a loss of compression and horsepower because the valvesare held off their seats.

U.S. Pat. No. 5,860,398, Engine Tappet; and U.S Pat. No. 5,947,069,Roller Type Mechanical Tappet, both issued to the inventor of theinvention herein described, and both herein incorporated by reference,are directed to a tappet structure that includes a roller bearinglocated between an upper and a lower race, the races and roller bearinglocated between the foot of the tappet and the body of the tappet. Theinvention presented in these two patents differs from the invention herein that the roller bearing and races are not used in this invention. Inthis invention one difference, in one embodiment, is that the foot ofthe tappet is placed proximate the bottom of the tappet and spaced apartfrom it by a film of oil that creates a hydrocushion between the top ofthe foot and the bottom of the body of the tappet. In this structure thecost and complication of the roller bearing and races has beeneliminated thus providing a less expensive and less complicated tappetwith a rotatable foot portion that will interface with a cam of acamshaft. In a second embodiment of the invention the roller bearing iseliminated and a thrust washer is located between the top of the footand the bottom of the body of the tappet. In this situation ahydrocushion of oil is formed between the top of the thrust washer andthe body of the tappet and also between the bottom of the thrust washerand the top of the foot. This embodiment is focused on in the followingdescription of the invention.

Thus, the need exists for a new form of lifter or tappet that combinesthe many advantages of the different types of lifters or tappets withlittle or none of their varied disadvantages. Thus, a need exists for amultiple piece; roller-type mechanical tappet for use in highperformance applications and that is effective, reliable, andinexpensive to produce.

SUMMARY OF THE INVENTION

It is an object of this invention to overcome many problems typicallyassociated with prior art valve train designs.

It is an object of this invention to provide a tappet device thatreduces friction between the tappet foot and the lobe of the camshaft.

It is an object of this invention to provide a multi-piece lifter ortappet having one end that rotates on the face of the cam.

It is an object of this invention to provide a lifter or tappet that isboth durable and reliable.

It is an object of this invention to provide a lifter or tappetcomprising interchangeable components.

It is an object of this invention to provide a mechanical tappet withinterchangeable tappet feet to adapt to a variety of cam shaft materialsand designs.

It is an object of this invention to provide a mechanical tappet withinterchangeable push rod receiver cups.

It is an object of this invention to provide a mechanical tappet withinterchangeable receiver cups of different thicknesses, and that can bechanged to change overall push rod lengths.

It is an object of this invention to provide a mechanical tappet havinga light-weight body section, and a hardened base section capable ofenduring substantial frictional forces.

It is an object of this invention to provide a mechanical tappet thatcan be used effectively with camshafts having steep opening and closingflank angles.

It is an object of this invention to provide a mechanical tappet that iscost effective to produce.

It is an object of this invention to provide a mechanical tappet thatwill increase engine horsepower.

It is an object of this invention to provide a mechanical tappet thatrequires little, or no, break-in time.

It is an object of this invention to provide a mechanical tappet that iseasily adapted to a rev kit by linking consecutive pairs of tappets.

It is an object of this invention to provide a mechanical tappetincluding a lubrication system that supplies increased lubrication tothe valves and valve springs.

It is an object of this invention to provide a mechanical tappetincluding a lubrication system that supplies increased lubrication tothe cam lobes of the cam shaft.

It is an object of this invention to decrease operating engine oiltemperatures by increasing tappet performance and lubrication, whilereducing valve train friction.

It is an object of this invention to provide a mechanical tappet thatcan be used in all major racing classes.

It is an object of this invention to provide a mechanical tappet that iseasy to install, remove and break-in.

It is an object of this invention to be able to provide a mechanicaltappet able to endure substantial valve spring pressures.

It is an object of this invention to be able to be adapted for use witha hydraulic tappet.

It is an object of this invention to be able to be adapted for use withan overhead direct acting bucket tappet.

The above and other objects are achieved by a tappet comprising a foothaving a convex cam contact surface and an axially extending hub and atappet body having a lower body portion with a lower axial bore formedtherein to receive the axially extended hub of the foot. The cam contactsurface operates in a frictional relationship with a cam lobe of arotating cam. The frictional relationship between the cam lobe and thecam contact surface of the foot induces the foot to rotate about thecenterline of the tappet. A hydrocushion of oil between the flat topsurface of the foot and a flat lower surface of the tappet body operatesto reduce friction as the foot independently rotates axially about acenterline of the tappet body.

The foot is removable from the lower bore in the tappet body. The camcontact, or bottom surface of the foot can be formed with a profile thatmatches or compliments a corresponding profile of the cam with which itcooperates to enhance efficiency between the cam and the foot.

The tappet includes a replaceable push rod receiver cup assemblysupported by a top portion of the tappet body. The top portion of thetappet body includes an upper axial bore and a support shelf formedwithin the bore, and the replaceable push rod receiver cup assembly issupported on the support shelf within the bore in the top portion of thetappet body. In a preferred form, the push rod receiver cup comprises aspacer and a mated receiver cup.

The tappet includes an oil delivery system forming an oil path leadingfrom the tappet body to the upper surface of the foot and to the convexcam contact surface of the foot. The oil delivery system also includesan oil path leading from the tappet body to the push rod receiver cupassembly. In one form, the oil delivery system includes an oil accessorifice formed in the mid-section of the tappet body at a locationselected to mate with a source of oil, wherein the orifice leads to aninterior chamber of the tappet body. A first oil orifice is formed inthe foot to provide a hydrocushion of oil between the top surface of thefoot and the bottom surface of the lifter. An oil supply orifice mayalso be provided on the foot to assist in lubricating the foot to camlobe interface. A bore is formed in the center of the axially extendinghub of the foot and serves as a passage between the interior chamber ofthe tappet body and the first oil orifice for providing the hydrocushionof oil between the lower surface of the tappet and the flat uppersurface and the second orifice for lubricating the cam lobe surface. Anoil channel is also formed in the spacer of the push-rod receiver cupassembly, and an oil orifice is formed in the base of the push rodreceiver cup. Oil is received from a source in the motor, and isdelivered to the oil orifices in the foot and replaceable push rod cup.

The aspects and applications of the invention presented here aredescribed below in the drawings and detailed specification. Unlessspecifically noted, it is intended that the words and phrases in thespecification and the claims be given the plain, ordinary and accustomedmeaning to those of ordinary skill in the applicable arts. The inventorsare fully aware that they can be their own lexicographers if desired.The inventors expressly elect, as their own lexicographers, to use onlythe plain and ordinary meaning of terms in the specification and claimsunless they clearly state otherwise and then further, expressly setforth the “special” definition from that term and explain how it differsfrom the plain and ordinary meaning. Absent such clear statements ofintent to apply a “special” definition, it is the inventors' intent anddesire that the simple, plain and ordinary meaning to the terms beapplied to the interpretation of the specification and claims.

The inventors are also aware of the normal precepts of English grammar.Thus, if a noun, term or phrase is intended to be further characterizedor specified, or narrowed in some way, then such noun, term or phrasewill expressly include additional adjectives, descriptive terms or othermodifiers in accordance with the normal precepts of English grammar.Absent the use of such adjectives, descriptive terms or modifiers, it isthe intent that the such nouns, terms or phrases be given their plainand ordinary English meaning to those skilled in the applicable arts asset forth above.

Further, the inventors are fully informed of the standards andapplication of the special provisions of 35 U.S.C. 112, Paragraph 6.Thus, the use of the words “function,” “means” or “step” in the DetailedDescription or Description of the Drawings or claims is not intended tosomehow indicate a desire to invoke the special provisions of 35 U.S.C.112, Paragraph 6, to define the invention. To the contrary, if theprovisions of 35 U.S.C. 112, Paragraph 6 are sought to be invoked todefine the inventions, the claims will specifically and expressly statethe exact phrases “means for” or “step for,” and will also clearlyrecite “a function” (i.e., will state “means for performing the functionof [insert function]”), without also reciting in such phrases anystructure, material or act in support of the function. Thus, even whenthe claims recite a “means for performing the function of . . . ” or“step for performing the function of . . . . , ” if the claims alsorecite any structure, material or acts in support of that means or step,or that perform the recited function, then it is the clear intention ofthe inventors not to invoke the provisions of 35 U.S.C. 112, Paragraph6. Moreover, even if the provisions of 35 U.S.C. 112, Paragraph 6 areinvoked to define the claimed inventions, it is intended that theinventions not be limited only to the specific structure, material oracts that are described in the preferred embodiments, but in addition,include any and all structures, materials or acts that perform theclaimed function as described in alternative embodiments or forms of theinvention, or that are well known present or later-developed, equivalentstructures, material or acts for performing the claimed function.

BRIEF DESCRIPTION OF THE DRAWINGS

The characteristics and benefits of the present invention can be moreeasily understood from the following descriptions of the preferredembodiments in combination with the accompanying drawings.

FIG. 1 is a perspective side view showing a typical tappet and camapplication in a push rod engine in its ignition or compression cycle.

FIG. 2 is a perspective side view showing a typical tappet and camapplication in a push rod engine in its intake or exhaust cycle.

FIG. 3 is an expanded apart view of a preferred embodiment of theinvention.

FIG. 3A is a sectional side view of an intermediate spacer andinterchangeable push rod receiver cup used with the present invention.

FIG. 3B is an alternative embodiment where a thrust washer is not used.

FIG. 4 is a fragmentary elevation view depicting the tappet as itappears in its bore, and showing the relationship between the tappetfoot and the cam lobe.

FIG. 5 is an assembly view of another embodiment of the device in whichan off-set push rod cup and anti-rotational strap are used.

FIG. 6 is an assembly view of another embodiment of the inventionemploying a “Rev Kit.”

FIG. 7 is a cut away side view of another embodiment of the device as itappears in use with a hydraulic lifter.

FIG. 8 is a cut away side view of another embodiment of the invention asit appears in use with an overhead direct acting bucket tappet.

DESCRIPTION OF THE INVENTION

The purpose and operation of a tappet or lifter is well known in theart. A tappet is a device designed to work in direct relation with arotating camshaft for the purpose of opening and closing intake andexhaust valves in an internal combustion engine. There are basicallyfour types of tappets; mechanical, mushroom, hydraulic, and rollertappets. The present invention pertains primarily to a form ofmechanical tappet in a uniquely modified form.

FIG. 1 is a partial side view representing a conventional tappet and camarrangement with valve 8 in the closed position, indicating that theengine cylinder is in either the ignition or compression cycle. A foot10 of tappet 12 is in direct contact with a foot 14 (sometimes referredto as heel) of a cam 13. The opposite end of the tappet body 12 containsa push rod receiver cup 18 that receives spherical end 20 of a push rod22. The opposing spherical end 24 of push rod 22 is pivotally receivedinto a receiver cup 26 of a rocker arm 28. The rocker arm 28 is mountedon a rocker arm shaft 30. The valve end 32 of the rocker arm 28 is indirect contact with a valve stem end 34. Located beneath the valve stemend 34 is a spring retainer 36 and a valve spring 38. The valve spring38 is a compression spring and exerts constant pressure on cylinder headsurface 40 and a spring retainer 36 when the valve is closed. A valveface 42 comprises machined chamfered radial edge that forms a positiveseal 46 with a valve seat 47 of an intake exhaust port 48. The valvehead is a flat surface on the bottom of the valve and forms the top of acompression chamber 50. The valve 8 remains in the closed position aslong as the cam foot 10 of tappet 12 is in contact with the cam footportion 14 of cam 13, causing the valve spring 38 to exert force on thespring retainer 36, causing the entire valve train assembly to shift inthe direction of the arrows, thus holding the valve 8 in the closedposition.

FIG. 2 depicts valve 8 in an open position, which occurs during theintake or exhaust cycle of the cylinder. Cam 13 rotates until the raisedcam lobe 16 is positioned under cam foot 10 of tappet 12. The lobe 16lifts the tappet 12 upward, forcing the push rod 22 to cause the rockerarm 28 to pivot on rocker arm shaft 30. The valve end 32 of rocker arm28 presses against valve stem top 34, causing valve spring 38 tocompress and the valve 8 to open, as illustrated by the direction of thearrows.

FIGS. 1 and 2 collectively illustrate the basic operation of the valvetrain of a push rod internal combustion engine, including the manner inwhich the valves open and close. The opening and closing processperpetuates itself as long as fuel, spark, and air are supplied to thecombustion chamber. This process is fundamental to the operation of aninternal combustion engine.

FIG. 3 is a perspective view of a preferred embodiment of the improvedtappet of the invention. The components identified in Section A of FIG.3 is referred to below as the foot section of the tappet. The footsection includes an interchangeable foot 10 and a flat thrust washer 65.The foot section further (referring additionally to FIG. 4) comprises aconvex hardened surface 54. In operation, the hardened surface 54remains in contact with the tapered surface 56 at contact surface 58(indicated by the circular track) of cam lobe 13 on camshaft 17. Thecontact surface 58 is located off-center in relation to the centerline60 of interchangeable cam foot 10. This offset relationship causes theinterchangeable foot 10 to axially rotate about the centerline 60 of thetappet 62 (as indicated by the arrow E shown in FIG. 4) when cam 13begins to rotate about its longitudinal axis (as indicated by the arrowD shown in FIG. 4). Because of the multi-piece design, foot 10 rotatesseparately from lifter body 62, as discussed in further detail below.

The independent axial rotation of the foot 10 relative to the flatthrust washer 65 and lifter body 62 is an important improvement in theinvention that helps to reduce the negative effects of friction. Tofurther reduce frictional forces, a small hole 64, as seen in FIG. 4, isdrilled or otherwise formed through the center of foot 19 to allow thepassage of oil to lubricate cam lobe 13. The foot 10 is interchangeable,thereby allowing custom applications that cover a wide variety ofcamshaft designs and requirements. Specifically, another feature of theinvention is the ability to design matched tappet foot 10 and cam lobeprofiles 56 for specific applications. This is facilitated by allowingthe replacement of one specific foot 10 with another having either adifferent diameter such as a mushroom tappet, or made of a differentmaterial in order to adapt to a variety of camshaft designs. The foot 10of the tappet includes a raised hub 66 that extends axially along thecenterline 60 from a flat bearing race surface 68. The axial hub 66 isslidably received into the bore 84 of a tappet bushing 76. A lubricationpassage 85 may be formed on the interior of the bore 84 to allowlubrication of the interior of the bore and to allow lubricant to flowto the top of the thrust washer 65, the bottom of the thrust washer andthe flat upper surface 68 of the tappet foot.

It should be pointed out that the thrust washer 65 has a centralaperture that is very slightly larger than the diameter of the raisedhub 66. That is the thrust washer central aperture may be only a smallincrement larger, for instance in the range of a few ten thousands of aninch to several ten thousands of an inch more than that, than thediameter of the raised hub. The aperture is also provided with at leastone, and preferable two, very small oil passages, running the thicknessof the thrust washer from the top service to the bottom surface of thethrust washer. These very small oil passages allow oil to flow to thetop and to the bottom of the thrust washer and thus allow a film of oil,forming a hydrocushion of oil between the top surface of the thrustwasher and the bottom of the main body. A hydrocushion of oil will alsobe formed between the bottom of the thrust washer and the top of thefoot 10. Thus two hydrocushions of oil will be formed between the topsurface of the foot and the bottom of the main body of the tappet.

Returning to FIG. 3, the end of raised axial hub 66 may contain, in oneembodiment and as shown in this figure, a threaded hole 78 that receivesretention screw 80. The retention screw 80 extends vertically downwardthrough a retaining washer 82. The retaining washer 82 has a largerouter diameter than inside bore 84 of bushing 76. As will become clearbelow, retention screw 80 operates to hold the foot Section A to theremainder of the tappet 12 when it is installed and removed from theengine. During operation, retention screw 80 is not needed because thetappet 12 is held in place naturally between rotating cam lobe 10 andpush rod 22.

An alternative embodiment of the invention shown in FIG. 3 is shown inFIG. 3B. This embodiment does not include the thrust washer mentionedabove. In this alternative embodiment a flat upper surface 68 of thefoot 10 is separated from contact with the lower flat surface 88 of thelifter body 62 by a hydrocushion of oil between the surfaces.

In FIG. 4 the two hydrocushions of oil will be formed. Thesehydrocushions are between surface 88 and the upper surface of the thrustwasher 65 and between the bottom of the thrust washer 65 and the surfaceof the foot 68 in the area generally identified as F.

As shown in FIG. 4, the cam bushing 76 is press fit into the axial bore90 in the lower portion of the lifter body 62 as it is in theembodiments shown in FIGS. 3-5.

In the various embodiments, when the cam shaft 17 begins to rotate, thefoot 10 also begins to axially rotate due to the relationship betweenthe tapered surface 56 of the cam 13 and the convex cam surface 54discussed above and shown in FIG. 4. The hydrocushions of oil betweenthe surfaces of the thrust washer 65, in the interface between the uppersurface of the foot and the lower surface of the lifter body 88 in areaF greatly reduces friction as the tappet foot 10 rotates. Morespecifically, instead of requiring rotation of the entire tappetassembly (including the elongated tappet body 62), the foot 10 rotatesindependently from the lifter body 62 separated by the hydrocushions ofoil or in the case of the embodiment shown in FIG. 3B, the singlehydrocushion of oil. Because the foot 10 is smaller and lighter than theentire tappet assembly, including the body 62, and further, rotatesaxially on the hydrocushions of oil less friction is generated betweenthe camshaft 17 and foot 10, thereby greatly increasing performance.Performance is even further increased as a result of the lubricationsystem (as discussed in greater detail below) and the interchangeablefeatures of the tappet foot 10.

The components shown in Section B of FIG. 3 are referred to as the“lifter body portion,” and comprises the main lifter body 62, thebushing 76, and the push rod cup 18. The lifter body 62 is a separateassembly from foot Section A. It can therefore be made of alighter-weight material than the foot section to still further reducethe forces of friction. The bottom of the lifter body contains axialbore 90, which receives cam foot bushing 76, typically in a press fitrelationship. Approximately mid-way up the body 62 of the lifter is aradial grooved recess 94, which operates as an oil relief or liftergallery. Depending on the application desired, oil orifice 96 can bedrilled within the radial grooved recess 94, or slightly above it. If itis drilled within the radial groove 94 it functions as an inertia valvelifter. If the oil orifice is drilled slightly above the radial groove94 it functions as an edge orifice lifter.

An inertia valve lifter receives oil from an oil gallery in the engineblock through orifice 96. Once the oil is inside the lifter, an inertiaactivated, flapper-type, one way valve (not shown) forces the oil totravel up through a pushrod orifice 102 and down through the footorifice 64. In essence, the lifter actually acts as a miniature oil pumpand provides more oil pressure and volume to the upper valve train. Theoil port 96 on an edge orifice lifter (as discussed above) is locatedslightly above the radial grooved recess 94. In an edge orifice lifter,the oil from the supply gallery enters the lifter through small orifice96 in much the same way as in the inertia valve lifter. However,additional oil passes around the lifter and down to subsequent liftersin the lifter bank. Because the orifice is located high on the lifterbody, it is not exposed to the high pressure in the lifter gallery, andthe amount of oil admitted is restricted by the clearance between thelifter bore and the lifter. Because of that fact, an edge orifice liftertypically delivers approximately 20% less oil to the top end of theengine than an inertia-valve lifter. In both types of lifters, once oilenters the lifter body, it flows upward through the lifter body 62,around intermediate spacer 98, through an oil port 100 formed in thebottom of the push rod receiver cup 18 through bored push rod oilchannel 102 formed in the bottom of the push rod 22, and through thepush rod oil channel 102 to the top end of the engine. The presentinvention is compatible and functions equally well with either aninertia-valve lifter or an edge-orifice lifter because interchangeablefoot 10 can be used with either type of lifter. Therefore, the inventionis not restricted to only one type of mechanical tappet.

If additional lubrication is desired between the tapered cam surface 56and convex hardened surface 54, the present invention provides alubrication port 64 located at the center foot 10 (See FIG. 4, but thisport may also be included but not shown in the other figures.). Oil canthen flow through to oil port 64 via hole 81 drilled through retentionscrew 80.

The intermediate spacer 98 is slidably received into the top of thelifter body 62, and rests on a radial edge 104 machined or otherwiseformed in the inside of the lifter body 62. The spacer 98 contains alaterally grooved channel 106 located on its top surface of theintermediate spacer 98. The diameter of intermediate spacer 98 isslightly smaller than inside diameter 108 of the lifter body, therebyallowing lubricating oil to flow around the spacer 98 into the groovedchannel 106, through orifice 100 in the pushrod receiver cup 18, throughpushrod orifice 102, and into pushrod 22, eventually reaching the top ofthe engine valve train.

Also slidably received into the top of lifter body 62 is aninterchangeable pushrod receiver cup 18. The bottom surface of pushrodreceiver cup 18 is in direct contact with the top surface ofintermediate spacer 98, thus creating channel 106 (see FIG. 3A) throughwhich lubrication oil flows. Snap ring 110 is received into a radialgroove (not shown) formed on the inside surface of the lifter body 62,thereby holding intermediate spacer 98 and pushrod receiver cup 18within lifter body 62. Thus, another advantage of the invention is theuse of a separate pushrod receiver cup 18, thereby allowing theselection from among cups of different thickness to be installed for thepurpose of changing the overall pushrod length if desired.

As discussed above, FIG. 4 depicts a fragmentary elevation side view ofthe assembled device in operation. Tappet or lifter foot 10 is shown incontact with tapered cam surface 56. As tapered cam lobe surface 56rotates in direction of arrow

D as driven by a cam chain or gear (not shown), the lifter foot 10rotates axially about the centerline of the lifter body 62, as shown bythe direction of arrow E. The rotation of the foot 10 is completelyindependent from lifter body 62. This independent rotation is madepossible because of the off center orientation between the hardenedconvex surface 54 and tapered cam surface 56, and the hydrocushions ofoil on each side of the thrust washer 65. It should be understood fromFIG. 4 that the principles of the invention apply equally to any form oftappet, including a bucket-type, hydraulic, or other form of tappet, aslong as the foot is allowed to rotate separately from the tappet body atthe interface with the cam lobe. In the application of the invention fora bucket-type tappet, the tappet is inverted on a valve spring so thatthe rotating foot contacts the lobe of an overhead cam.

FIG. 5 represents alternative embodiment of the preferred device. It issimilar to the embodiment shown in FIG. 3, but is modified in order touse high seat, offset pushrod cup 122, or a Rev Kit (not shown). In someengine configurations (especially configurations in which the intakeports have been bored larger) it is desirable, if not necessary; to havean offset pushrod receiver cup 122 to prevent the pushrod fromcontacting the engine block as it moves up and down. Thus, in thismodified form of the invention, pushrod receiver cup 122 must retain thesame orientation with; respect to the engine manifold. The lifters musttherefore incorporate an anti-rotational device. In order to prevent thelifters from rotating, an anti-twist link bar 116 is attached toconsecutive lifter bodies by retainer screws 118 and 120 into respectivethreaded holes, thereby preventing the pair of lifters from rotating.One anti-rotation strap is necessary for each pair of lifters.

FIG. 6 depicts still another embodiment of the invention that employs aRev Kit. A Rev Kit functions as a counter spring and maintains aconstant downward force on the lifter body to help keep the foot 10 incontact with the tapered cam surface 56 of cam 13. This is particularlybeneficial in high-rpm applications. In the embodiment depicted in FIG.6, radial lip 128 of adapter 126 is slidably received into the top oflifter body 62. Counter spring 130 is likewise received into a radialgroove 132 machined into the top of adapter 126. Spring holder 134 ispositioned in such a way so as to receive the top of compression spring130 into a machined radial groove 136. Pushrod 22 is then receivedthrough spring holder 134, counter spring 130, adapter 126, and intopushrod receiver cup 18 on top of lifter body 62.

Shown in simplified schematic form in FIG. 7 is a modified form of theinvention as employed in a hydraulic tappet. Shown in simplifiedschematic form in FIG. 8 is yet another modified form of the inventionas applied to a bucket tappet for use with an overhead cam. In each ofthese Figures, like numerals indicate like parts as shown in the earlierFigures. Specifically, in each of these modified embodiments, the foot10 rotates on a hydraulic cushions of oil about the centerline of thetappet body, as induced by friction between the tapered cam surface 56of the cam 13.

One embodiment of the invention can be summarized as a tappet with afoot having a convex cam contact surface an axially extending hub, atappet body having a lower body portion with a lower axial bore formedtherein to receive the axially extended hub of the foot; and ahydrocushion of oil between the foot and the lower portion of the tappetbody, the hydrocushion of oil operating to reduce friction as the footseparately rotates axially about a center line of the tappet body. Thetop of the foot is a flat surface and the bottom of the lower portion ofthe tappet body is a flat surface separated from the top surface of thefoot by the hydrocushion of oil.

In this embodiment the hydrocushion of oil reduces friction between therotating foot and the tappet body.

The apparatus set forth above is summarized in that it includes a tappetcomprising a foot having a convex cam contact surface an axiallyextending hub, a thrust washer carried on the extending hub of the footand a tappet body having a lower body portion with a lower axial boreformed therein to receive the axially extended hub of the foot. Ahydrocushion of oil between the foot and the thrust washer and ahydrocushion of oil between the thrust washer and the lower portion ofthe tappet body provides for free rotation as the hydrocushions of oilreduce friction between the rotating foot, the thrust washer and thetappet body.

The foot, the top of the foot being a flat surface and the thrustwasher, having a flat bottom surface are removable from the lower borein the tappet body. The bottom of the thrust washer is separated fromthe top of the foot by a hydrocushion of oil while the top surface ofthe thrust washer is separated from the bottom surface of the lowerportion of the tappet body by a hydrocushion of oil.

In further summary one aspect of the invention is a method of making atappet that comprises forming a foot having a cam contact surface and anaxially extending hub. A thrust washer, having a central aperture andoil passage on the central aperture, is located on the axially extendinghub. A tappet body is formed and has a lower body portion with a loweraxial bore formed therein to accept the axially extending hub of thefoot. A first hydrocushion of oil is formed between the foot and thethrust washer and a second hydrocushion of oil if formed between thethrust washer and the tappet body.

Furthermore the method also comprises providing oil under pressure tothe site of the first cushion of oil through the lower axial bore of thetappet body and providing oil under pressure to the site of the secondcushion of oil through the lower axial bore of the tappet body andthrough the oil passages of the thrust washer. The method also comprisesproviding a tappet bushing with a through bore, in the lower axial boreof the lower body portion of the tappet body and forming an oil passageon the through bore extending from one end of the tappet bushing to theother end of the bushing. In this method a top flat surface is formed tosupport the thrust washer on a hydrocushion of oil, and the lowerportion of the tappet body includes a lower flat surface formed tocontact a hydrocushion of oil between the thrust washer and the lowerportion of the tappet body. Also the act of forming an oil passage fromthe tappet body to the top surface of the thrust washer and to thebottom surface of the thrust washer is contemplated by the inventor.

In its preferred form, the disclosed tappet device offers manyimprovements over the prior art. For example, because of itsmultiple-piece design, friction is greatly reduced between the lifterfoot and the cam lobe because only the lifter foot is rotating. Also,the preferred device may be used effectively with camshafts having steepopening and closing flank angles necessary in high performanceapplications. Also due to the decreased friction, operating engine oiltemperatures will be significantly reduced. In addition, because of themultiple piece design, a lighter weight lifter body can be used with ahardened lifter foot. The preferred form of the device also allows forinterchangeable push rod receiver cups of different thicknesses so pushrods need not be changed to alter their length, only the push rodreceiver cup. Further, lubrication to the cam lobes and camshaft will beincreased because of the drilled through hole on the lifter foot. Also,the device in its preferred form can be used in all racing classes inaddition to any and all stock applications. Still other advantages willbe readily apparent to those who use the device. As mentioned above, theinvention can be employed on any form of tappet, including mechanical,mushroom, hydraulic and bucket type tappets.

1. A tappet comprising: a foot having a convex cam contact surface anaxially extending hub; a tappet body having a lower body portion with alower axial bore formed therein to receive the axially extended hub ofthe foot; and a hydrocushion of oil between the foot and the lowerportion of the tappet body, the hydrocushion of oil operating to reducefriction as the foot separately rotates axially about a center line ofthe tappet body.
 2. The tappet of claim 1 wherein the cam contactsurface operates in a frictional relationship with a cam lobe of arotating cam, and wherein the frictional relationship between the camlobe and the cam contact surface of the foot induces the foot to rotateabout the centerline of the tappet.
 3. The tappet of claim 1 wherein thefoot is removable from the lower bore in the tappet body.
 4. The tappetof claim 1 wherein the hydrocushion of oil reduces friction between therotating foot and the tappet body.
 5. The invention in accordance withclaim 1 wherein the top of the foot is a flat surface and the bottom ofthe lower portion of the tappet body is a flat surface separated fromthe top surface of the foot by the hydrocushion of oil.
 6. A tappetcomprising: a foot having a convex cam contact surface an axiallyextending hub; a thrust washer carried on the extending hub of the foot;a tappet body having a lower body portion with a lower axial bore formedtherein to receive the axially extended hub of the foot; and ahydrocushion of oil between the foot and the thrust washer; ahydrocushion of oil between the thrust washer and the lower portion ofthe tappet body.
 7. The tappet of claim 6 wherein the cam contactsurface operates in a frictional relationship with a cam lobe of arotating cam, and wherein the frictional relationship between the camlobe and the cam contact surface of the foot induces the foot to rotateabout the centerline of the tappet.
 8. The tappet of claim 6 wherein thefoot and the thrust washer are removable from the lower bore in thetappet body.
 9. The tappet of claim 6 wherein the hydrocushions of oilreduce friction between the rotating foot, the thrust washer and thetappet body.
 10. The invention in accordance with claim 6 wherein thetop of the foot is a flat surface, the thrust washer has a flat bottomsurface, and the bottom of the thrust washer is separated from the topof the foot by a hydrocushion of oil.
 11. The invention in accordancewith claim 6 wherein the bottom of the lower portion of the tappet bodyis a flat surface, the thrust washer has a flat top surface, and the topsurface of the thrust washer is separated from the bottom surface of thelower portion of the tappet body by a hydrocushion of oil.
 12. A methodof making a tappet comprising the acts of: forming a foot having a camcontact surface and an axially extending hub; locating a thrust washerhaving a central aperture and oil passage on the central aperture on theaxially extending hub; forming a tappet body having a lower body portionwith a lower axial bore formed therein to accept the axially extendinghub of the foot; forming a first hydrocushion of oil between the footand the thrust washer; forming a second hydrocushion of oil between thethrust washer and the tappet body.
 13. The method of claim 12 furthercomprising providing oil under pressure to the site of the first cushionof oil through the lower axial bore of the tappet body.
 14. The methodof claim 12 further comprising providing oil under pressure to the siteof the second cushion of oil through the lower axial bore of the tappetbody and through the oil passages of the thrust washer.
 15. The methodof claim 12 further comprising; providing a tappet bushing, having athrough bore, in the lower axial bore of the lower body portion of thetappet body; forming an oil passage on the through bore extending fromone end of the tappet bushing to the other end of the bushing.
 16. Theinvention in accordance with claim 12 further comprising forming aconvex surface on the surface of the cam contact surface.
 17. Theinvention in accordance with claim 12 wherein the foot includes a topflat surface formed to support the thrust washer on a hydrocushion ofoil, and the lower portion of the tappet body includes a lower flatsurface formed to contact a hydrocushion of oil between the thrustwasher and the lower portion of the tappet body.
 18. The invention inaccordance with claim 12 further comprising the act of forming an oilpassage from the tappet body to the top surface of the thrust washer andto the bottom surface of the thrust washer.